A case before Vanuatu's Supreme Court implicating 18 of the nation's MPs in bribery has taken a dramatic twist as finance minister Willie Jimmy entered a guilty plea on two counts on Wednesday.

The defendants, 14 of which are on trial, are accused of accepting bribes amounting to 35 million vatu ($447,000) and breaching the parliament's leadership code. All but Jimmy entered pleas of not guilty.

The high-profile defendants include the deputy prime minister, Moana Carcasses, and five ministers of state.

"It's fair to say he appeared quite confused, and we also need to have explained why his lawyer was not present in court, which Justice Mary Sey — the presiding judge — was fairly annoyed about," he said.

"She did give him an opportunity though, she suggested to him that if he didn't speak at all she would record a not guilty plea. And he said 'oh, in that case I'll plead guilty' to the shock of the entire court.

"Of course, he could well turn up at the next hearing on Monday, with a lawyer present, and say 'look, I was confused, I didn't have legal counsel at the time and I'd like the plea changed'.

"And I think the court would look fairly favourably at that."

The 18 MPs of the 52-seat parliament are alleged to have taken bribes from the now-deputy prime minister a year ago while in opposition.

Carcasses has always stated the money was transferred to the parliamentarians as a loan, into their private accounts, for use in their constituencies.

Vanuatu politics is often paralysed by no-confidence motions and a high turnover of its leadership, and the money is alleged to have been used to procure support before an attempt to remove the then-prime minister Joe Natuman.